In the brush seal, for example as are used in gas turbines between the stator and the rotor, it is known that swirling fluid arrives at the brush seal on the high pressure side and this will tend to cause the bristles to be deflected in a generally axial direction at the free ends causing the bristles to bend upwardly away from the rotor. The effect is believed to be dependent on the velocity of the swirling fluid.
As an initial approach to reducing this problem for some time, people have positioned a front plate onto the brush seal assembly, which can have the effect of reducing bristle deflection, but it is only successful to a limited extent, because on current designs there has to be a fairly significant gap between the free end of the front plate and, say, the rotor shaft.